Method of forming an underlayer for extreme ultraviolet (euv) dose reduction and structure including same

ABSTRACT

Methods of forming structures including a photoresist absorber layer and structures including the absorber layer underlying an extreme ultraviolet (EUV) photoresist are disclosed. Exemplary methods include forming the photoresist absorber layer or underlayer with an oxide of a high atomic number (z) element having an EUV cross section (σ α ) of greater than 2×10 6  cm 2 /mol and then forming the EUV photoresist over the high-z underlayer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 63/240,664 filed Sep. 3, 2021, titled METHOD OF FORMING ANUNDERLAYER FOR EXTREME ULTRAVIOLET (EUV) DOSE REDUCTION AND STRUCTUREINCLUDING SAME, the disclosure of which is hereby incorporated byreference in its entirety.

FIELD OF INVENTION

The present disclosure generally relates to structures and to methodsused in the formation of devices. More particularly, the disclosurerelates to structures including or formed using a photoresist absorberlayer (sometimes referred to as an underlayer or UL) with improvedextreme ultraviolet (EUV) absorbance to facilitate EUV dose reductionand to methods of forming such structures.

BACKGROUND OF THE DISCLOSURE

During the manufacture of electronic devices, fine patterns of featurescan be formed on a surface of a substrate by patterning the surface ofthe substrate and etching material from the substrate surface using, forexample, gas-phase etching processes. As a density of devices on asubstrate increases, it generally becomes increasingly desirable to formfeatures with smaller dimensions.

Photoresist is often used to pattern a surface of a substrate prior toetching. A pattern can be formed in the photoresist by applying a layerof photoresist to a surface of the substrate, masking the surface of thephotoresist, exposing the unmasked portions of the photoresist toradiation, such as ultraviolet light, developing the exposed orunexposed portions of the photoresist to remove a portion (e.g., theunmasked or masked portion) of the photoresist, while leaving a portionof the photoresist on the substrate surface.

Recently, techniques have been developed to use extreme ultraviolet(EUV) wavelengths to develop patterns having relatively small patternfeatures. One limitation of methods using EUV is the relatively low fluxof EUV photons and the resultant long exposure times and/or theinadequate exposure of the photo-sensitive materials that areresponsible for creating contrast between exposed and unexposed areas ofthe photoresist.

Accordingly, structures for lowering EUV dose requirements and methodsof forming such structures are desired. Any discussion of problems andsolutions set forth in this section has been included in this disclosuresolely for the purpose of providing a context for the present disclosureand should not be taken as an admission that any or all of thediscussion was known at the time the invention was made.

SUMMARY OF THE DISCLOSURE

Various embodiments of the present disclosure relate to structuresincluding improved photoresist absorber layers (sometimes referred to asunderlayers) and to methods of forming the layers and structures. Whilethe ways in which various embodiments of the present disclosure addressdrawbacks of prior methods and structures are discussed in more detailbelow, in general, various embodiments of the disclosure providestructures that include a photoresist absorber layer with relativelyhigh EUV sensitivity. The relatively high sensitivity allows for use ofa relatively low dosage of EUV to obtain desired contrast betweenexposed and unexposed areas of the photoresist, which, in turn, allowsfor the formation of features with desired properties, such as smallcritical dimensions, which can be formed in a relatively cost-effectivemanner. In addition, only needing a relatively low dosage of EUVadvantageously allows reducing exposure times, thereby increasingthroughput of EUV exposures.

Exemplary EUV absorber layers or underlayers include an element withrelatively high EUV absorption. In some embodiments, an oxide of such anelement (or a metal oxide) is formed, which can be used as an EUVabsorption-enhancing underlayer for EUV lithography, for example. Suchabsorber layers can be stand alone or part on an underlayer film stack.Use of such absorber layers can provide desired patterned featuresduring EUV photoresist patterning, using relatively low EUV dosageduring a step of exposing the photoresist to EUV radiation. Exemplaryunderlayers, e.g., oxides of high-z elements such as I, Te, Cs, Sb, Sn,In, Bi, Ag, Pb, Au, Pt, and Ir (with oxides of Sn or In being desirablein some implementations), can be formed using a cyclical process, suchas atomic layer deposition (ALD) or plasma-enhanced atomic layerdeposition, which allows for precise control of a thickness of thephotoresist absorber layer—both on a surface of a substrate and fromsubstrate to substrate.

The underlayers are primarily based on an oxide of an element having ahigh (e.g., 45 or higher) atomic number (z), but the underlayers mayalso be doped with other high z elements (which may be chosen for havinga photoabsorption cross section at 91.5 eV on a per mole basis less than5×10⁶ cm²/mol (or relatively high EUV sensitivity on a molar basis)and/or with lighter elements (which may be chosen for having aphotoabsorption cross section at 91.5 eV on a per mass basis greaterthan 8×10⁵ cm²/g (or relatively high EUV sensitivity on a mass basis)).

In accordance with exemplary embodiments of the disclosure, a method isprovided for forming an extreme ultraviolet (EUV) absorber layer on asurface of a substrate. The method includes providing a substrate withina reaction space of a gas-phase reactor, providing a precursor to thereaction space, and providing a reactant to the reaction space. Themethod also includes the step of forming an absorber layer on a surfaceof the substrate within the reaction space, and the absorber layerincludes an element having an EUV cross section (σ_(α)) of greater than2×10⁶ cm²/mol. In other embodiments, the precursor includes a compoundaccording to the following formula: MR, where M is selected from Cs, Sb,Sn, In, Bi, Ag, Pb, Au, Pt, and Ir, wherein R is a C1 to C4 alkyl, andwhere n is from at least 3 to at most 5.

According to some embodiments of the method, the absorber layer furtherincludes a dopant selected from the group consisting of I, Te, Cs, Sb,Sn, In, Bi, Ag, Pb, Au, Pt, and I or from the group consisting of I, Te,Cs, Sb, In, Bi, Ag, Pb, Au, Pt, and I. In these or other cases, theabsorber layer further includes a dopant selected from the groupconsisting of Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Hf, and As. In theseimplementations, the absorber layer includes an underlayer and a layerincluding the dopant overlying or underlying the underlayer.

The step of forming the absorber layer may include a cyclical depositionprocess. The step of forming the absorber layer may involve atomic layerdeposition. The method also may include forming an EUV photoresist layeroverlying the absorber layer. In these or other embodiments, the methodmay include the step of forming an adhesion layer overlying the absorberlayer to limit outgassing from the adhesion layer and facilitateadhesion of the absorber layer to the EUV photoresist layer.

According to other aspects of the description, a structure is providedfor forming patterned features using extreme ultraviolet (EUV)radiation. The structure may include a substrate and an absorber layerformed overlying the substrate. The absorber layer may include an oxideof I, Te, Cs, Sb, Sn, In, Bi, Ag, Pb, Au, Pt, or Ir. The structure mayalso include an EUV photoresist layer formed overlying the absorberlayer. In some embodiments of the structures, the absorber layerincludes tin oxide or indium oxide.

In these or other embodiments of the structure, the absorber layerincludes a dopant selected from the group consisting of I, Te, Cs, Sb,Sn, In, Bi, Ag, Pb, Au, Pt, and (or, in some cases, the group consistingof Ir I, Te, Cs, Sb, In, Bi, Ag, Pb, Au, Pt, and I) and/or from thegroup consisting of Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Hf, and As. Thestructure may also include a dopant layer underlying or overlying theabsorber layer. The dopant layer may include at least one elementselected from the group consisting of I, Te, Cs, Sb, Sn, In, Bi, Ag, Pb,Au, Pt, and Ir and/or may include at least one element selected from thegroup consisting of Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Hf, and As.Additionally, the structure may include an adhesion layer overlying theabsorber layer to limit outgassing from the adhesion layer andfacilitate adhesion of the absorber layer to the EUV photoresist layer.

In accordance with further examples of the disclosure, a system isprovided. The system can be used to perform a method described hereinand/or to form a structure as described herein.

These and other embodiments will become readily apparent to thoseskilled in the art from the following detailed description of certainembodiments having reference to the attached figures; the invention notnecessarily being limited to any particular embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

A more complete understanding of exemplary embodiments of the presentdisclosure can be derived by referring to the detailed description andclaims when considered in connection with the following illustrativefigures.

FIG. 1 illustrates a method in accordance with exemplary embodiments ofthe disclosure.

FIG. 2 illustrates a structure in accordance with exemplary embodimentsof the disclosure.

FIG. 3 illustrates a system configured for executing a method asdescribed herein.

FIG. 4 is a graph showing EUV exposure doses (or exposure energy) duringtesting of an underlayer of the present description including a tinoxide.

FIG. 5 is a graph showing EUV exposure doses (or exposure energy) duringtesting of an underlayer of the present description including an indiumoxide.

FIG. 6 is a side view of an underlayer stack used to provide a dopant toenhance EUV sensitivity showing a sandwich approach.

FIG. 7 is a side view of another underlayer stack used to providedopants to enhance EUV sensitivity using a laminate mix approach.

FIG. 8 illustrates a direct plasma system for executing a method asdescribed herein.

FIG. 9 illustrates an indirect plasma system for executing a method asdescribed herein.

FIG. 10 illustrates a remote plasma system for executing a method asdescribed herein.

It will be appreciated that elements in the figures are illustrated forsimplicity and clarity and have not necessarily been drawn to scale. Forexample, the dimensions of some of the elements in the figures may beexaggerated relative to other elements to help improve understanding ofillustrated embodiments of the present disclosure.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The description of exemplary embodiments of the present inventionprovided below is merely exemplary and is intended for purposes ofillustration only; the following description is not intended to limitthe scope of the invention disclosed herein. Moreover, recitation ofmultiple embodiments having stated features is not intended to excludeother embodiments having additional features or other embodimentsincorporating different combinations of the stated features.

The present disclosure generally relates to methods of formingstructures that include an extreme ultraviolet (EUV) absorber layer (orunderlayer (UL)) and to structures including the EUV absorber layer.Exemplary methods can be used to form structures with underlayers(absorber layers) with increased EUV sensitivity, which can result inlower EUV dosages used during photoresist exposure steps. The methodscan be used to form structures with EUV absorber layers that allow forformation of patterned features with desired properties, such as smallcritical dimensions, reduced tapering and/or reduced roughness, comparedto photoresist features formed using typical EUV photolithographytechniques. Thus, methods described herein can provide for increasedthroughput of the manufacture of structures, reduced costs associatedwith the formation of the structures and/or devices formed using thestructures, and/or a reduction of critical dimensions of features formedusing the absorber layer and the photoresist layer.

As used herein, the term substrate may refer to any underlying materialor materials including and/or upon which one or more layers can bedeposited. A substrate can include a bulk material, such as silicon(e.g., single-crystal silicon), other Group IV materials, such asgermanium, or compound semiconductor materials, such as GaAs, and caninclude one or more layers overlying or underlying the bulk material.For example, a substrate can include a patterning stack of severallayers overlying bulk material. The patterning stack can vary accordingto application and can include, for example, a hardmask, such as a metalhardmask, an oxide hardmask, a nitride hardmask, a carbide hardmask, oran amorphous carbon hardmask. Further, the substrate can additionally oralternatively include various features, such as recesses, lines, and thelike formed within or on at least a portion of a layer of the substrate.

In some embodiments, film refers to a layer extending in a directionperpendicular to a thickness direction. In some embodiments, layerrefers to a material having a certain thickness formed on a surface or asynonym of film or a non-film structure. A film or layer may beconstituted by a discrete single film or layer having certaincharacteristics or multiple films or layers, and a boundary betweenadjacent films or layers may or may not be clear and may or may not beestablished based on physical, chemical, and/or any othercharacteristics, formation processes or sequence, and/or functions orpurposes of the adjacent films or layers. Further, a layer or film canbe continuous or discontinuous.

In this disclosure, gas may include material that is a gas at normaltemperature and pressure, a vaporized solid and/or a vaporized liquid,and may be constituted by a single gas or a mixture of gases, dependingon the context. A gas other than the process gas, i.e., a gas introducedwithout passing through a gas distribution assembly, such as ashowerhead, other gas distribution device, or the like, may be used for,e.g., sealing the reaction space, and may include a seal gas, such as anoble gas.

As used herein, Cp stands for cyclopentadienyl, Me stands for methyl, Etstands for ethyl, Bu stands for butyl, and iPr stands for isopropyl.

In some cases, such as in the context of deposition of material, theterm precursor can refer to a compound or compounds that participates inthe chemical reaction that produces another compound, and particularlyto a compound that constitutes a film matrix or a main skeleton of afilm, whereas the term reactant can refer to a compound, in some casesother than precursors, that reacts with the precursor, activates theprecursor, modifies the precursor, or catalyzes a reaction of theprecursor; a reactant may provide an element (e.g., a halide) to a filmand become a part of the film. In some cases, the terms precursor andreactant can be used interchangeably. The term inert gas refers to a gasthat may or may not take part in a chemical reaction and/or a gas thatdoes interact with a precursor and/or reactant when, for example, aplasma is formed, but unlike a reactant, it may not become a part of afilm matrix to an appreciable extent.

The term cyclic deposition process or cyclical deposition process mayrefer to the sequential introduction of precursors (and/or reactants)into a reaction chamber to deposit a layer over a substrate and includesprocessing techniques such as atomic layer deposition (ALD), cyclicalchemical vapor deposition (cyclical CVD), and hybrid cyclical depositionprocesses that include an ALD component and a cyclical CVD component. Inother cases, the processing techniques may include a plasma process suchas plasma enhanced CVD (PECVD) or plasma enhanced ALD (PEALD), which maybe preferred in some implementations because they allow working at lowertemperatures. Plasma processes may be desirable as they use chemicalprecursors, such as in thermal ALD, but these processes also cycle anRF-plasma creating the necessary chemical reactions in a highlycontrolled manner.

The term atomic layer deposition may refer to a vapor deposition processin which deposition cycles, typically a plurality of consecutivedeposition cycles, are conducted in a process chamber. The term atomiclayer deposition, as used herein, is meant to include processesdesignated by related terms, such as chemical vapor atomic layerdeposition, atomic layer epitaxy (ALE), molecular beam epitaxy (MBE),gas source MBE, or organometallic MBE, and chemical beam epitaxy whenperformed with alternating pulses of precursor(s)/reactive gas(es), andpurge (e.g., inert carrier) gas(es).

Generally, for ALD processes, during each cycle, a precursor isintroduced to a reaction chamber and is chemisorbed to a depositionsurface (e.g., a substrate surface that can include a previouslydeposited material from a previous ALD cycle or other material), formingabout a monolayer or sub-monolayer of material that does not readilyreact with additional precursor (i.e., a self-limiting reaction).Thereafter, in some cases, a reactant may subsequently be introducedinto the process chamber for use in converting the chemisorbed precursorto the desired material on the deposition surface. The reactant can becapable of further reaction with the precursor. Purging steps can beutilized during one or more cycles, e.g., during each step of eachcycle, to remove any excess precursor from the process chamber and/orremove any excess reactant and/or reaction byproducts from the reactionchamber.

As used herein, the term purge or purging may refer to a procedure inwhich gas flow is stopped or a procedure involving continual provisionof a carrier gas whereas precursor flow is intermittently stopped. Forexample, a purge may be provided between a precursor pulse and areactant pulse, thus avoiding, or at least reducing, gas phaseinteractions between the precursor and the reactant. It shall beunderstood that a purge can be effected either in time or in space orboth. For example, in the case of temporal purges, a purge step can beused, e.g., in the temporal sequence of providing a precursor to areactor chamber, providing a purge gas to the reactor chamber, andproviding a reactant to the reactor chamber, wherein the substrate onwhich a layer is deposited does not move. In the case of spatial purges,a purge step can take the form of moving a substrate from a firstlocation to which a precursor is supplied, through a purge gas curtain,to a second location to which a reactant is supplied.

In this disclosure, any two numbers of a variable can constitute aworkable range of the variable, and any ranges indicated may include orexclude the endpoints. Additionally, any values of variables indicated(regardless of whether they are indicated with about or not) may referto precise values or approximate values and include equivalents, and mayrefer to average, median, representative, majority, etc. in someembodiments. Further, in this disclosure, the terms including,constituted by and having can refer independently to typically orbroadly comprising, comprising, consisting essentially of, or consistingof in some embodiments. Further, the term comprising can includeconsisting of or consisting essentially of. In accordance with aspectsof the disclosure, any defined meanings of terms do not necessarilyexclude ordinary and customary meanings of the terms.

Turning now to the figures, FIG. 1 illustrates a method 100 inaccordance with exemplary embodiments of the disclosure. Method 100 canbe used for forming an extreme ultraviolet (EUV) absorber layer orunderlayer on a surface of a substrate. Method 100 includes the steps ofproviding a substrate within a reaction space of a gas-phase reactor(step 102), providing a precursor to the reaction space (step 104),providing a reactant to the reaction space (step 106), and forming anabsorber layer (step 108). Method 100 can also include a step of formingan EUV photoresist layer (step 110) overlying the absorber layer.

Exemplary methods can be or include cyclical deposition methods, such asALD methods, and can include, in some useful embodiments, indirect,direct, and remote plasma methods, which may include super cycleprocesses in which sub-cycles may be selectively repeated to enhancetuning (e.g., to achieve a desired amount or concentration of a desiredelement in the absorber or underlayer or the like). The high-zunderlayers described herein can be formed using CVD, thermal ALD,PECVD, or PEALD. The steps 104, 106, and 108 may be performedcontemporaneously in some desirable implementations of the method 100and/or in differing orders. For example, the steps of exposing thesubstrate to precursor and reactant may be performed either in analternating or simultaneous manner, and this results in absorberformation such that absorber may occur contemporaneously with precursorand reactant exposure.

Step 102 includes providing a substrate, such as a substrate describedherein, within a reaction space of a gas-phase reactor. The substratecan include one or more layers, including one or more material layers,to be etched. By way of examples, the substrate can include a depositedoxide, a native oxide, or an amorphous carbon layer to be etched. Thesubstrate can include several layers underlying the material layer(s) tobe etched.

During step 104, a precursor is provided to the reaction space.Exemplary precursors can include one or more (e.g., metallic) elementswith a relatively high EUV cross section (σ_(α)) greater than 2×10⁶cm²/mol. For example, the precursor can include I, Te, Cs, Sb, Sn, In,Bi, Ag, Pb, Au, Pt, Ir, or the like. The method 100 may be performed tocreate an underlayer based on a metal oxide, with oxides of elementssuch as Sn, In, and the like being useful in some embodiments of method100. In some embodiments, the precursor includes a compound according tothe following formula: M(NR¹R²)_(n), where M is selected from Cs, Sb,Sn, In, Bi, Ag, Pb, Au, Pt, and Ir or from the group consisting of Cs,Sb, In, Bi, Ag, Pb, Au, Pt, and Ar, where R₁ and R2 are independentlyselected from H and C1 to C4 alkyl, and where n is from at least 3 to 5.In other exemplary embodiments, the precursor includes a compoundaccording to the following formula: MR_(n), wherein M is selected fromCs, Sb, Sn, In, Bi, Ag, Pb, Au, Pt, and Ir, where R is a C1 to C4 alkyl,and where n is from at least 3 to at most 5.

By way of particular examples, the precursor can include one or more aprecursor comprising one or more alkylamine ligands such astetrakis(diethylamino)tin, a precursor comprising one or more metalbeta-diketonate ligands, a precursor comprising one or more alkoxideligands, a precursor comprising one or more amidinate ligands, aprecursor comprising one or more alkyl ligands, a precursor comprisingone or more hydrogen ligands, a precursor comprising a combination ofhydrogen and alkyl ligands such as 1H, 3 alkyl ligands (e.g., when theabsorber layer includes an oxide of Sn), a precursor comprisingcyclopendanienyl (Cp) ligands, and a precursor comprising one or morealkylaminopropoxide ligands, such as dimethylaminopropoxide ligands(e.g., when the absorber layer includes an oxide of In), a precursorcomprising one or more halide ligands such as SbCl₃, and a precursorcomprising one or more alkylsilyl ligands such as Te(TMS)₂ (e.g., when adopant of SbTe is deposited above or below the absorber layer asdiscussed below with reference to FIGS. 6 and 7 ), or the like.

In some implementations of the method 100, the precursors may compriseligands including cyclopentadienyl, alkylamide, alkoxide, alkyl,alkylsylyl, halide, amidinate, diazadiene, and carbonyl ligands. In somecases, the metal precursor comprises an alkylamido compound. Exemplarymetal alkylamido compounds include a metal center and one or moreindependently selected (e.g., C1-C4) alkyl amine ligands. Particularexamples include M(NMe₂)₄, M(NEt₂)₄, and M(NEtMe)₄.

Exemplary metal alkoxide compounds include M(OMe)₄, M(OEt)₄, M(OiPr)₄,M(OtBu)₄, MO(OMe)₃, MO(OEt)₃, MO(OiPr)₃, and MO(OtBu)₃. Additional metalalkoxide compounds include variations of these compounds, where otheralkoxy ligands are used.

Exemplary metal cyclopentadienyl compounds include MCp₂Cl₂, MCp₂, andMCp₂(CO)₄. Additional exemplary cyclopentadienyl compounds includevariations of these compounds, where Cp is either unsubstituted orbearing one or more alkyl groups, e.g., MeCp, EtCp, iPrCp, and the like.

By way of particular examples, the precursor can include one or more ofa metal halide, such as a Pb halide (e.g., PbF₂), a Sb halide (e.g.,SbCl₃), a Bi halide (e.g., BiCl₃, BiF₃, BiI₃), an indium halide (e.g.,InF₃, InCl₃); a metal silylamide, e.g., a metal bis(trimethylsilyl)amide(btsa) (e.g., Pb-silylamide (e.g., Pb(btsa)₂)), a Bi-silylamide (e.g.,Bi(btsa)₂); a metal trimethylsily precursor (e.g., Te(TMS)₂); a metalalkoxide (e.g., cesium tert-butoxide (CsO^(t)Bu), a Bi-alkoxide,antimony(III) ethoxide (Sb(OEt)₃); a metal amine or amino precursor,such as Bi(NMe₂)₃, Bi(NEtMe)₃), Sb(NMe₂)₃, Pb[N(SiMe₃)₂]₂; a metalcyclopentadienyl precursor (e.g., InCp); an alkyl metal precursor, suchas trimethylindium (TMI), triethylindium (TEI), or the like.

By way of additional examples, a metal alkylsilylamide or metalsilylamide compound can be represented by the general formula (i), whereR1-R6 are each independently selected from a C1-C4 alkyl group.

A wide variety of Sn precursors may be utilized. For example, theprecursor may be a halide such as SnCl₄, SnBr₄, or SnI₄. In other cases,the precursor may be an alkoxide such as Sn(OR)₄, where R can beindependently any of the following: methyl, ethyl, n-propyl, isopropyl,n-butyl, sec-butyl, isobutyl, and tert-butyl. In other exemplaryembodiments, the precursor may be an alkylamide such as Sn(NR₂)₄, whereR can be independently any of the following: methyl, ethyl, n-propyl,isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, trimethylsilyl,triethylsilyl, or Sn(NR₂)₂, where R can be independently trimethylsilylor triethylsilyl. The precursor may also be an alkyl such as SnR₄,SnHR₃, SnH₂R₂, and SnH₃R, where R can be independently any of thefollowing methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl,isobutyl, tert-butyl, n-pentyl, neopentyl, tert-pentyl, cyclopentyl,n-hexyl, cyclohexyl, phenyl, vinyl, and allyl. A diketonates may also beused such as SnL₂ or SnL₄, where L is a beta-diketonate ligand such asacetylacetonate, 2,2,6,6-tetramethylhexane-3,5-diketonate,1,1,1,5,5,5-hexafluoroacetylacetonate, and the like. In other cases, theprecursor is an amidinates such as Sn(iPr₂FMD)₂, Sn(tBu₂FMD)₂,Sn(iPr₂AMD)₂, and Sn(tBu₂AMD)₂, where FMD is formamidinate and AMD isacetamidinate.

Further, the precursor may take the form of a chelating aminoalkoxidessuch as Sn(dmap)₂, Sn(dmamp)₂, Sn(dmamb)₂, where R1 is H or Me, andR2-R4 are independently any C1 to C6 hydrocarbyl group and as given byEquation (ii) below and where dmap: R1=H, R2=R3=R4=methyl, dmamp:R1=R2=R3=R4=methyl, or dmamb: R1=ethyl, R2=R3=R4=methyl.

Likewise, a wide variety of Sn precursors may be utilized. For example,the precursor may be a halide such as InCl₃, InCl, InClMe₂, or InBr₃. Analkyls may be used such as InMe₃, InEt₃, InEtMe₂, Me₂In(CH₂)₃NMe₂,In(N(SiMe₃)₂)Et₂, In(N(SiMe₃)₂)Me₂ InMe₂(dmap), InMe₂(dmamp), orInMe₂(dmamb). Diketonates may be used as the In precursor such as InL₃,where L is a beta-diketonate ligand such as acetylacetonate,2,2,6,6-tetramethylhexane-3,5-diketonate,1,1,1,5,5,5-hexafluoroacetylacetonate, and the like. The precursor mayalso be a cyclopentadienes such as InCp, In(EtCp), or indium compoundscomprising other alkyl substituted Cp ligands. In other embodiments, theprecursor is a chelating aminoalkoxide such as In(dmap)₃, In(dmamp)₃,In(dmamb)₃; InMe₂(dmap), InMe₂(dmamp), InMe₂(dmamb), orIn(dmamb)₂(OiPr). Amidinates may be used for the precursor such asIn(iPr₂FMD)₃, In(tBu₂FMD)₃, In(iPr₂AMD)₃, and In(tBu₂AMD)₃, where FMD isformamidinate and AMD is acetamidinate.

Additionally, a wide variety of Sb precursors may be utilized. Forexample, the precursor may be a halide such as SbCl₃, SbCl₅, SbBr₃, orSbI₃. The Sb precursor may be an alkylsilyl such as Sb(SiMe₃)₃ orSb(SiEt₃)₃. Alkylamides may be used for the Sb precursor such asSb(NR₂)₃, where R can be independently any of the following: methyl,ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl,trimethylsilyl, and triethylsilyl. Additionally, the Sb precursor may bean alkoxides such as Sb(OR)₃, where R can be independently any of thefollowing: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl,isobutyl, and tert-butyl.

With regard to Te precursors, the precursor may be a halide such asTeCl₄, TeF₆, TeBr₄, or TeI₄. The precursor may also be an alkyl such asTeR₂ where R can be independently any of the following methyl, ethyl,n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl,neopentyl, tert-pentyl, cyclopentyl, n-hexyl, cyclohexyl, phenyl, vinyl,and allyl. An alkylsilyl may be used for the Te precursor such asTe(SiMe₃)₂ or Te(SiEt₃)₂. In some embodiments, the Te precursor may bean alkylgermyl such as Te(GeMe₃)₂ or Te(GeEt₃)₂. Further, the Teprecursor may take the form of an alkoxide such as Te(OR)₄, where R canbe independently any of the following: methyl, ethyl, n-propyl,isopropyl, n-butyl, sec-butyl, isobutyl, and tert-butyl.

A temperature within a reaction space during step 104 can be, forexample, between about 20° C. and about 200° C. A pressure within thereaction chamber during step 104 can be about 140 Pa to about 1300 Pa. Aflowrate of the precursor can be between about 200 to about 2000 sccm. Aduration of a pulse of introducing the precursor to the reaction chambercan be between about 0.1 and about 15 seconds.

During step 106, a reactant is provided to the reaction space. Inaccordance with examples of the disclosure, the reactant includes ahalide, such as one or more of F, Cl, Br, and I. Particular exemplaryhalides suitable for use as a reactant include HF, TiF₄, SnI₄, CH₂I₂,HI, I₂, and the like. In some cases, another precursor can be areactant. In such cases, the reactant can include any of the precursorsnoted above.

In addition, oxygen reactants, nitrogen reactants, carbon reactants, andreducing reactants may be used. Suitable oxygen reactants include O₂,O₃, and H₂O. Suitable nitrogen reactants include N₂, NH₃, N₂H₂, andforming gas. Suitable carbon reactants include alkyls such as CH₄.Suitable reduction reactants include H₂. If other elements are desired,the reactant may be chosen to suit the need. For example, to Te isdesired, one could us Te(OR)₄, Te(TMS)₂, dialkyltellurides (such asTe(iPr)₂, Te(tBu)₂, and the like) or elemental Te, where R stands for analkyl such as a low C alkyl (e.g., one containing 1 to 4 C atoms), whereTMS stands for trimethylsilyl, where TES stands for triethylsilyl (ormore broadly for trialkylsilyl), where, for S, one could use H₂S,dialkylsulfide, dialkyldisulfide, alkylthiol, (TMS)₂S, S₂Cl₂, orelemental S, and where, for Se, one could use H₂Se, alkylselenol,dialkylselenide, dialkyldiselenide, bis(trialkylsilyl)selenide, orelemental Se. The precursor may be an acetate such as Sn(OAc)₄ orSnBu₂(OAc)₂, where OAc is the acetate ligand. In some embodiments, theprecursory is a cyclic amide of Sn(II) such as(1,3-bis(1,1-dimethylethyl)-4,5-dimethyl-(4R,5R)-1,3,2-diazastannolidin-2-ylidene).

A temperature and pressure within the reaction chamber during step 106can be the same or similar to the temperature and/or pressure notedabove in connection with step 104. A flowrate of the reactant can bebetween about 100 to about 2000 sccm. A duration of a pulse ofintroducing the reactant to the reaction chamber can be between about0.1 and about 30 seconds. As illustrated in FIG. 1 , steps 104 and 106can be repeated one or more times to form the absorber layer (step 108).Various combinations of precursors and corresponding reactants suitablefor use in steps 104 and 106 can be used to form the absorber layer. Forexample, in some cases, the absorber layer includes an oxide, such as ametal oxide of Sn, In, or the like.

In some cases, the absorber layer comprises an oxide of a high-z element(e.g., an element with an atomic number over 45) such as one selectedfrom the group consisting of F, Mg, Na, Al, Mn, Fe, Co, Ni, Cu, Zn, Ga,Ge, and As. In accordance with other examples, the absorber layer isdoped (e.g., during step 104, 106, and/or 108) to include a dopant ormaterial useful for increasing the EUV sensitivity. For example, someembodiments of the method 100 include doping the absorber layer withanother element with a high atomic number (z), which also has a high EUVabsorption on a per mole basis, e.g., a EUV cross section (σ_(α))greater than 2×10⁶ cm²/mol. These dopants may be selected so as toinclude one or more of F, Mg, Na, Al, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge,and As. In these or alternative embodiments of method 100, the dopantmay be a lighter element or low-z element that can be chosen due to itsrelatively high EUV sensitivity on a mass basis (e.g., an element with aphotoabsorption cross section at 91.5 eV on a per mass basis greaterthan 8×10⁵ cm²/g or higher), such as one or more of Mn, Fe, Co, Ni, Cu,Zn, Ga, Ge, and As and with F, Na, Mg, and Al being preferred in somecases.

The absorber layers which are described herein may, for example, bedeposited using a thermal cyclical (e.g., ALD) or a thermal CVD method.Alternatively, the absorber layers that are described herein may bedeposited using cyclical plasma (e.g., plasma ALD) or plasmapulsed-CVD—e.g., by activating (directly or remotely) a reactant and/orprecursor. Both approaches may suitably provide for the deposition ofthin (5 nm) absorber layers with low non-uniformity.

Particular examples of materials suitable for the absorber layer areprovided above. A thickness of the absorber layer formed during step 104can be in the range of 1 to 10 nm, with 2 to 5 nm being useful in somecases and with 2 to 3 nm used in some embodiments of structures with ametal oxide underlayer as described herein.

As illustrated in FIG. 1 , once a desired thickness of the absorberlayer via steps 104-108 is obtained, an optional EUV photoresist layercan be formed over the absorber layer (e.g., in direct contact with theabsorber layer) during step 110. In such implementations of the method,the EUV photoresist layer may include any suitable photoresist, such asmolecular, metal oxide, or chemically amplified photoresist. Inaddition, it may be desirable to etch or strip the absorber layer fromthe substrate surface. Therefore, the absorber layer may desirablyinclude material that can form soluble or volatile compounds whenreacted with an etchant.

FIG. 2 illustrates a structure 200 in accordance with exemplaryembodiments of the disclosure. Structure 200 can be formed using, forexample, method 100. As illustrated, structure 200 includes a substrate202, an absorber layer 204, and optionally one or more of a materiallayer 208, and a photoresist layer 206. Material layer 208 and EUVphotoresist layer 206 can be used to provide desired stability toabsorber layer 204 and/or for other reasons. Substrate 202 can include asubstrate as described above. By way of examples, substrate 202 caninclude a semiconductor substrate and can include one or more layers.Further, as noted above, substrate 202 can include various topologies,such as recesses, lines, and the like formed within or on at least aportion of a layer of the substrate.

Absorber layer 204 can include an absorber layer formed in accordancewith a method described herein (e.g., method 100) and/or compriseabsorber material as described herein and/or have properties asdescribed herein. A thickness of absorber layer 204 can depend on acomposition of absorber layer 204, a thickness of and/or composition ofmaterial layer 208, a thickness of and/or composition of photoresistlayer 206, a type of photoresist, and the like. In accordance withexamples of the disclosure, absorber layer 204 has a thickness of lessthan 10 nm or less than or about 5 nm (such as 2 to 3 nm or more).

Material layer 208 can be formed of, for example, a hard mask. A hardmask can be any layer that provides etch contrast with the underlyinglayers. A commonly used hard mask is amorphous carbon. In otherembodiments, the material layer 208 may include metals, semiconductorsand their alloys, oxides, nitrides, and carbides. A thickness ofmaterial layer 208 can be from about 0.1 to about 10 nm. Photoresistlayer 206 can be formed of, for example, molecular resist, a metal oxideresist, or a chemically amplified resist. A thickness of photoresistlayer 206 can be from about 5 to about 40 nm.

FIG. 3 schematically illustrates a system 300 in accordance withexamples of the disclosure. System 300 can be used to perform a methodas described herein and/or to form a structure or a portion thereof asdescribed herein. In the illustrated example, system 300 includes one ormore reaction chambers 302, a precursor injector system 301, a precursorvessel 304, a reactant vessel 306, an auxiliary reactant source 308, anexhaust source 310, and a controller 312. System 300 may include one ormore additional gas sources (not shown), such as an inert gas source, acarrier gas source and/or a purge gas source. Reaction chamber 302 caninclude any suitable reaction chamber, such as an ALD or CVD reactionchamber as described herein.

Precursor vessel 304 (sometimes a metal precursor vessel) can include avessel and one or more precursors as described herein including metalprecursors—alone or mixed with one or more carrier (e.g., inert) gases.Reactant source vessel 306 can include a vessel and one or morereactants (e.g., oxide reactants, halide reactants, and the like) asdescribed herein— alone or mixed with one or more carrier gases. In somecases, it will be understood that some reactants, such as O₂, N₂, Hz,He, and Ar, are very common and are used throughout a fabrication.Accordingly, they may not be necessarily stored in a vessel inside thetool but may, instead, be provided from a central storage unit (notshown, which may be a pressurized vessel) via gas lines to the tools inthe fabrication system 300. Auxiliary reactant source 308 can include anauxiliary reactant or a precursor as described herein. Althoughillustrated with three source vessels 304-308, system 300 can includeany suitable number of source vessels to provide the element with a highEUV absorption on a per mass basis and other materials, such as dopingmaterials, in some implementations. Source vessels 304-308 can becoupled to reaction chamber 302 via lines 314-318, which can eachinclude flow controllers, valves, heaters, and the like. In someembodiments, a vessel is heated so that a precursor or a reactantreaches a desired temperature. Each vessel may be heated to a differenttemperature, according to the precursor or reactant properties, such asthermal stability and volatility. Exhaust source 310 can include one ormore vacuum pumps.

Controller 312 includes electronic circuitry and software to selectivelyoperate valves, manifolds, heaters, pumps, and other components includedin system 300. Such circuitry and components operate to introduceprecursors, reactants, and purge gases from the respective sources.Controller 312 can control timing of gas pulse sequences, temperature ofthe substrate and/or reaction chamber 302, pressure within the reactionchamber 302, and various other operations to provide proper operation ofthe deposition or reactor system 300. Controller 312 can include controlsoftware to electrically or pneumatically control valves to control flowof precursors, reactants, and purge gases into and out of the reactionchamber 302. Controller 312 can include modules, such as a software orhardware component, which perform certain tasks. A module may beconfigured to reside on the addressable storage medium of the controlsystem and be configured to execute one or more processes.

In the illustrated example, system 300 also includes a gas distributionassembly (e.g., a showerhead) 320 and a susceptor or substrate holder322 (which can include an electrode and/or a heater) for receiving andsupporting a substrate (e.g., a wafer). In accordance with some examplesof the disclosure, system 300 can also include a remote plasma unit 324to activate one or more reactants, precursors, and/or inert gases.

Other configurations of system 300 are possible, including differentnumbers and kinds of precursor and reactant sources. Further, it will beappreciated that there are many arrangements of valves, conduits,precursor sources, and auxiliary reactant sources that may be used toaccomplish the goal of selectively and in a coordinated manner feedinggases into reaction chamber 302. Further, as a schematic representationof a deposition system, many components have been omitted for simplicityof illustration, and such components may include, for example, variousvalves, manifolds, purifiers, heaters, containers, vents, and/orbypasses.

During operation of deposition assembly 300, substrates, such assemiconductor wafers (not illustrated), are transferred from, forexample, a substrate handling system to reaction chamber 302. Oncesubstrates are transferred to reaction chamber 302, one or more gasesfrom gas sources, such as precursors, reactants, carrier gases, and/orpurge gases, are introduced into reaction chamber 302. In someembodiments, the precursor is supplied in pulses, the reactant issupplied in pulses and the reaction chamber is purged betweenconsecutive pulses of precursor and reactant.

From the above discussion, it should be understood that the inventorswere attempting to design new UL materials of high sensitivity for use,for example, in the EUV spectral region in order to improve the EUVabsorbance and provide a cost efficient solution. The layers ofdifferent elements that have high EUV capture cross sections can beincluded, in some cases, in the stack to increase the EUV sensitivity.

In this regard, the inventors understood that it may be desirable toprovide an underlayer (or absorber layer) under a EUV photoresist layerto reduce the full exposure required or to provide desirable “dosereduction.” Further, the inventors determined that such an underlayercan be provided by forming an underlayer that is based on an oxide of ahigh-z element, which may be chosen due to its relatively high EUVabsorption (e.g., an element having an EUV cross section (σ_(α)) ofgreater than 2×10⁶ cm²/mol or the like). Generally, this high-z elementmay be chosen to be one of I, Te, Cs, Sb, Sn, In, Bi, Ag, Pb, Au, Pt,and Ir, with the following description presenting specific useful oxides(e.g., SnO_(x) and InO_(x)) with the understanding that these teachingscan be expanded to other metal oxides.

In one exemplary implementation of the teaching herein, the underlayeris formed to include or be based mainly upon tin oxide. During testing,the SnO_(x) layer showed EUV dose reduction even for thinner films(e.g., films with thicknesses of 2 nm and 3 nm or films with a thicknessin range of 2 to 5 nm). The precursor used to form the underlayer filmson the substrate was tetrakis(diethylamino)tin, and an EUV photoresistwas formed over each of the underlayer films.

FIG. 4 illustrates a graph 400 showing with lines 410, 420, and 430 EUVdoses when an underlayer was provided underlying a EUV photoresist(e.g., a photoresist with a thickness of 35 nm). Particularly, line 410illustrates measured doses for a reference silicon underlayer while line420 illustrates doses for a 3 nm thick underlayer of tin oxide and line430 illustrates doses for a 2 nm thick underlayer. This testing shows adose reduction for such thinner films can be provided with a high-zunderlayer. The exposure dose 420 and 430 at which resist clears SnO_(x)shows the shifts left towards lower dose value than reference 410 solesser dose is required to develop the photoresist. The testing showedfull photoresist development, and a smooth and amorphous film surface onthe underlayer, which is good for integration. Thinner photoresists(e.g., 40 nm or less with 35 nm used in some testing) have shown betterresponses, and tin oxide underlayer showed good adhesion and no orlittle collapse. For example, it may be useful to provide a minimumconcentration of Sn in the underlayer in the range of at least 10 to atmost 90 atomic percent.

In another exemplary implementation of the teaching herein, theunderlayer is formed to include or be based mainly upon indium oxide.During testing, the InO_(x) layer showed EUV dose reduction even forthinner films (e.g., films with thicknesses of 2 nm, 4 nm, and 10 nm orfilms with a thickness in range of 2 to 10 nm). The precursor used toform the underlayer films on the substrate was trimethylindium, and anEUV photoresist was formed over each of the underlayer films.

FIG. 5 illustrates a graph 500 showing with lines 510, 520, 530, and 540EUV doses (e.g., EUV exposure at ILT) when an underlayer was providedunderlying a EUV photoresist (e.g., a SEVR photoresist with a thicknessof 35 nm). Particularly, line 510 illustrates measured doses for areference silicon underlayer while line 520 illustrates doses for a 10nm thick underlayer of indium oxide, line 530 illustrates doses for a 4nm thick underlayer, and line 540 illustrates doses for a 2 nm thickunderlayer.

This testing again shows a dose reduction for such thinner films can beprovided with a high-z underlayer. The exposure dose 520, 530, and 540at which resist clears InO_(x) shows the shifts left towards lower dosevalue than reference 510 so lesser dose is required to develop thephotoresist. Work with an underlayer including indium oxide showed avery positive impact with 25 percent dose reductions (e.g., until below2 nm in some cases). The testing showed full photoresist development,and a smooth and amorphous film surface on the underlayer, which is goodfor integration. It is believed that it is mainly the top part of thehigh-z underlayer that contributes to the dose lowering (as thesecondary electrons are reabsorbed) such that thinner films can beeffectively utilized and are desirable. Particularly, thinner (andamorphous) films can be helpful in etch selectivity so it is beneficialthat thinner films such as those tested impact dose reduction. Forexample, it may be useful to provide a concentration of In in theunderlayer that is from 10 to 90 atomic percent, with a 30 atomicpercent of In used in one exemplary implementation.

As discussed above, it may be desirable to dope the underlayer toenhance the EUV absorbance. In some embodiments, the new underlayersbased on an oxide of a high-z element (e.g., a metal from the listingsprovided above) may be doped such as with Te, Sb, Sn, In, and the like.In other embodiments, an underlayer that may contain mostly Si, C, and Omay be doped to improve EUV absorbance and/or the underlayer may becombined in a sandwich having a thin dopant layer between underlayers.Si and C do not have high EUV absorbance, and O has higher absorbancebut not sufficient to provide desired levels of EUV dose requirements.

With these issues with common underlayers in mind, the inventorsdetermined that the photoemission cross sections of different atoms thatare higher than those of O (and, therefore, also of Si and C) could beincluded as a dopant in the underlayer composition to increase the EUVsensitivity. This can be used to provide material absorption at EUV byincorporating elements containing elements or atoms such as Te, Sb, Sn,In, and/or other high-z elements in the underlayer composition. Sincethe sensitivity is going to be predominantly dictated by the compositionand the presence of these high-z materials are an important factor. Thecomposition of these elements can be tuned as desired in the dopingmechanism. Providing these elements as dopants provides more freedom intuning as compared with use of a high-z layer with underlayer stacks.Due to the use of the doping process, the composition can more readilybe tuned to achieve a desired increase in EUV sensitivity, and, in somecases, one or more (matching or differing) dopant laminate layers may beused with the underlayer (e.g., with underlayers sandwiching the dopantlaminate layer, with dopant laminate layers sandwiching the underlayer,or with stacks of alternating dopant laminate layers and underlayers).

The introduction of high-z elements as dopants in an underlayer (e.g.,an underlayer as described above and/or in other underlayers such asones that are mostly silicon) provided a number of desirable benefits.It can be used to increase the EUV sensitivity of the underlayer, whichcan reduce the EUV dose required for developing EUV photoresistoverlying the underlayer. The dopants, e.g., high-z elements, may beprovided as layers (e.g., laminate layers) on one side of or on bothsides of (e.g., sandwiching) the underlayer. These doping designsincrease compositional tunability of the high-z elements. In someapplications, all the steps (e.g., all steps of method 100) can be donein a single reactor, and all steps may be done using a plasma processwith no need of thermal and plasma combination processes.

A variety of dopants may be used to increase the EUV sensitivity. Insome embodiments, dopants with high EUV absorption may be chosenincluding one or more of Te, Sb, Sn, In, I, Cs, and Bi. In the same orother embodiments, it may be useful to include dopants with moderate EUVabsorption including one or more of Ge, Ni, Cu, Co, Zn, and Hf. Thedopant compositions may be provided as a laminate mix (e.g., a Te, Sb,Sn, In, I, Sb, and Te laminate mix) or as oxides (e.g., oxides of Te andSb or other of the dopant elements).

There are a variety of approaches that can be used to provide thedopants for the underlayer, and the thicknesses of the dopant layer mayvary with each approach with the dopant layer thickness range of about0.3 to 5 nm being useful in some cases. A laminate approach may be usedproviding one or more dopants, and, in some cases, different dopantconcentrations in differing dopant layers, e.g., by changing thesub-cycles in the laminates (such as varying the sub-cycles ratio tomain cycles such as 1:1, 1:2, 1:2.5, 1:5, and 1:10). This approach isshown in FIG. 6 with underlayer stack 600 that includes alternatinglayers of underlayer 610 with dopant layers 620, 630, and 640, which maybe similar in composition (and the same or varying thicknesses) or, asshown, may be used to provide three differing dopants or dopantcompositions. A bi-layer approach may also be used such as by providingone or more dopants in a layer over or under an underlayer. A sandwichlayer approach may be used to provide one or more dopants in a dopantlayer that may be sandwiched between two underlayers.

This approach is shown in FIG. 7 with underlayer stack 700 that includesan underlayer 710 sandwiching a dopant layer 720. The doped underlayeror underlayer stack may be provided below the photoresist (as shown inFIG. 2 ) or may be above the photoresist in some cases or in between two(or more) photoresist layers. Note, the final structure may be either alaminate or a homogenous mixture. Forming a homogenous mixture caninclude alternatingly depositing layers of composition A and layers ofcomposition B followed by annealing to obtain a homogenous layer that isessentially a mixture of the two layers that were first formed.

The doped underlayer or underlayer stack may be provided in a structureusing a number of deposition types including thermal, sputtering, directplasma, indirect plasma, remote plasma, and radical. In many cases,direct plasma may be a preferred process for forming the underlay orunderlayer stack. For example, the underlayer and dopant may be formedusing H-plasma or Ar-plasma. In other cases, the underlayer may beformed using H- (or Ar-) plasma while the dopant is formed using Ar- (orH-) plasma. In many cases, an H-containing plasma will also contain Ar,but other noble gasses such as He may be used as well, either as analternative or in addition to argon. The processing arrangement may bedesigned as: X (underlayer/purge/H-plasma/purge)+Y (dopant/shortpurge/H-plasma/purge), with varying of the X:Y ratios (where X is themain cycle and Y is the sub-cycle for doping). In other cases, theprocessing arrangement may be designed as: X(underlayer/purge/H-plasma/purge)+Y (dopant/short purge/H-plasma/purge),with varying X-Y ratios (where X is the main cycle and Y is thesub-cycle for doping) and then having a top layer of thin underlayer forbetter uniformity. Separate reactors may be used to deposit the high-zdopant layer and underlayer or the same reactor may be used to depositthem or for doping the underlayer with high-z dopants. Two sources maybe used for doping the underlayer and for forming laminates. In othercases, though, three sources may be used in the tool to deposit thehigh-z layers and then some underlayer (e.g., three precursors SbCl₃,Te(TMS)₂, and underlayer precursors, with SbCl₃ and Te(TMS)₂ used todeposit SbTe as a dopant) or for laminate mix of different dopants.

The presence of high-z materials can lead to outgassing of some volatileproducts. To address this potential issue, the inventors determined thatthe outgassing could be prevented or at least reduced by including anadhesion layer in the structures described herein that include high-zmaterials. For example, the adhesion layer may be provided over the topof the absorber layer 204 of structure 200 in FIG. 2 (and be formed aspart of step 108 of method 100 of FIG. 1 or a separate step prior tostep 110) or overlying the top layer of underlayer stacks 600 and 700 ofFIGS. 6 and 7 .

The adhesion layer may be provided as a layer or film of glue such asSiOC with a thickness in the range of 0.3 to 2 nm (with it being usefulin some cases for the total underlayer including the glue layer to havea maximum thickness of less than about 5 nm), and it may be formed ordeposited using plasma-based depositions, such as cyclical ornon-cyclical PECVD techniques, or other techniques. The adhesion layermay also be useful in improving the adhesion with the photoresist (e.g.,layer 206 in structure 200 of FIG. 2 that may be formed in step 110 ofmethod 100 of FIG. 1 ). The adhesion layer, hence, could be included toact as a sealing layer/film to prevent or limit outgassing while alsoimproving adhesion. This layer also may enable use of more high-zmaterials, which otherwise may be limited in use as forming potentiallytoxic layers.

Direct, indirect, and remote plasma depositions can be used as well,either in ALD, CVD, hybrid mode, as shown in with the systems 800, 900,and 1000 in FIGS. 8-10 , respectively. Various pulsing schemes featuringsuper cycles made up of two separate sub-cycles can be used. Forexample, a PEALD process may tune concentrations or amounts of a desiredelement using a super cycle process (e.g., sub-cycle 1: In precursorpulse, O reactant pulse; sub-cycle 2: Sn precursor pulse, O reactantpulse; with each repeated as useful for tuning in on a desired amount ofany particular element).

FIG. 8 shows a schematic representation of an embodiment of a directplasma system 800 that is operable or controllable to perform thefabrication processes or methods as described herein. The system 800includes a reaction chamber 810 in which a plasma 820 is generated. Inparticular, the plasma 820 is generated between a showerhead injector830 and a substrate support 840 supporting a substrate or wafer 841.

In the configuration shown, the system 800 includes two alternatingcurrent (AC) power sources: a high frequency power source 821 and a lowfrequency power source 822. In the configuration shown, the highfrequency power source 821 supplies radio frequency (RF) power to theshowerhead injector, and the low frequency power source 822 supplies analternating current signal to the substrate support 840. The radiofrequency power can be provided, for example, at a frequency of 13.56MHz or higher. The low frequency alternating current signal can beprovided, for example, at a frequency of 2 MHz or lower.

Process gas comprising precursor, reactant, or both, is provided througha gas line 860 to a conical gas distributor 850. The process gas thenpasses via through holes 831 in the showerhead injector 830 to thereaction chamber 810. Whereas the high frequency power source 821 isshown as being electrically connected to the showerhead injector and thelow frequency power source 822 is shown as being electrically connectedto the substrate support 840, other configurations are possible as well.For example, in some embodiments (not shown), both the high frequencypower source and the low frequency power source can be electricallyconnected to the showerhead injector; both the high frequency powersource and the low frequency power source can be electrically connectedto the substrate support; or both the high frequency power source can beelectrically connected to the substrate support, and the low frequencypower source can be electrically connected to the showerhead injector.

FIG. 9 shows a schematic representation of another embodiment of anindirect plasma system 900 operable or controllable to perform themethods as described herein. The system 900 includes a reaction chamber910, which is separated from a plasma generation space 925 in which aplasma 920 is generated. In particular, the reaction chamber 910 isseparated from the plasma generation space 925 by a showerhead injector930, and the plasma 920 is generated between the showerhead injector 930and a plasma generation space ceiling 926.

In the configuration shown, the system 900 includes three alternatingcurrent (AC) power sources: a high frequency power source 921 and twolow frequency power sources 922, 923 (i.e., a first low frequency powersource 922 and a second low frequency power source 923). In theconfiguration shown, the high frequency power source 921 supplies radiofrequency (RF) power to the plasma generation space ceiling, the firstlow frequency power source 922 supplies an alternating current signal tothe showerhead injector 930, and the second low frequency power source923 supplies an alternating current signal to the substrate support 940.A substrate 941 is provided on the substrate support 940. The radiofrequency power can be provided, for example, at a frequency of 13.56MHz or higher. The low frequency alternating current signal of the firstand second low frequency power sources 922, 923 can be provided, forexample, at a frequency of 2 MHz or lower.

Process gas comprising precursor, reactant, or both, is provided througha gas line 960 that passes through the plasma generation space ceiling926 to the plasma generation space 925. Active species such as ions andradicals generated by the plasma 920 from the process gas pass viathrough holes 931 in the showerhead injector 930 to the reaction chamber910.

FIG. 10 shows a schematic representation of an embodiment of a remoteplasma system 1000 operable or controllable to perform the fabricationmethods or processes as described herein. The system 1000 includes areaction chamber 1010, which is operationally connected to a remoteplasma source 1025 in which a plasma 1020 is generated. Any sort ofplasma source can be used as a remote plasma source 1025, for example aninductively coupled plasma, a capacitively coupled plasma, or amicrowave plasma. In particular, active species are provided from theplasma source 1025 to the reaction chamber 1010 via an active speciesduct 1060 to a conical distributor 1050 via through holes 1031 in ashower plate injector 1030 to the reaction chamber 1010. Thus, activespecies can be provided to the reaction chamber in a uniform way.

In the configuration shown, the system 1000 includes three alternatingcurrent (AC) power sources: a high frequency power source 1021 and twolow frequency power sources 1022, 1023 (e.g., a first low frequencypower source 1022 and a second low frequency power source 1023). In theconfiguration shown, the high frequency power source 1021 supplies radiofrequency (RF) power to the plasma generation space ceiling, the firstlow frequency power source 1022 supplies an alternating current signalto the showerhead injector 1030, and the second low frequency powersource 1023 supplies an alternating current signal to the substratesupport 1040. A substrate 1041 is provided on the substrate support1040. The radio frequency power can be provided, for example, at afrequency of 13.56 MHz or higher. The low frequency alternating currentsignal of the first and second low frequency power sources 1022, 1023can be provided, for example, at a frequency of 2 MHz or lower.

In some embodiments (not shown), an additional high frequency powersource can be electrically connected to the substrate support. Thus, adirect plasma can be generated in the reaction chamber. Process gascomprising precursor, reactant, or both, is provided to the plasmasource 1025 by means of a gas line 1060. Active species such as ions andradicals generated by the plasma 1020 from the process gas are guided tothe reaction chamber 1010.

The example embodiments of the disclosure described above do not limitthe scope of the invention, since these embodiments are merely examplesof the embodiments of the invention. Any equivalent embodiments areintended to be within the scope of this invention. Indeed, variousmodifications of the disclosure, in addition to the embodiments shownand described herein, such as alternative useful combinations of theelements described, may become apparent to those skilled in the art fromthe description. Such modifications and embodiments are also intended tofall within the scope of the appended claims.

We claim:
 1. A method of forming an extreme ultraviolet (EUV) absorberlayer on a surface of a substrate, the method comprising the steps of:providing a substrate within a reaction space of a gas-phase reactor;providing a precursor to the reaction space; providing a reactant to thereaction space; and forming an absorber layer on a surface of thesubstrate within the reaction space, the absorber layer comprising anelement having an EUV cross section (σ_(α)) of greater than 2×10⁶cm²/mol.
 2. The method of claim 1, wherein the absorber layer comprisesan oxide of the element.
 3. The method of claim 1, wherein the elementis selected from the group consisting of: I, Te, Cs, Sb, Sn, In, Bi, Ag,Pb, Au, Pt, and Ir.
 4. The method of claim 1, wherein the element is Sn.5. The method of claim 1, wherein the precursor comprises a compoundaccording to the following formula: M(NR¹R²)_(n), wherein M is selectedfrom Cs, Sb, Sn, In, Bi, Ag, Pb, Au, Pt, and Ir, wherein R¹ and R² areindependently selected from H and C1 to C4 alkyl, and wherein n is fromat least 3 to
 5. 6. The method of claim 1, wherein the element is In. 7.The method of claim 1, wherein the precursor comprises a compoundaccording to the following formula: MR_(n), wherein M is selected fromCs, Sb, Sn, In, Bi, Ag, Pb, Au, Pt, and Ir, wherein R is a C1 to C4alkyl, and wherein n is from at least 3 to at most
 5. 8. The method ofclaim 1 wherein the absorber layer further comprises a dopant selectedfrom the group consisting of I, Te, Cs, Sb, Sn, In, Bi, Ag, Pb, Au, Pt,and Ir.
 9. The method of claim 1, wherein the absorber layer furthercomprises a dopant selected from the group consisting of Mn, Fe, Co, Ni,Cu, Zn, Ga, Ge, Hf, and As.
 10. The method of claim 8, wherein theabsorber layer includes an underlayer and a layer including the dopantoverlying or underlying the underlayer.
 11. The method of claim 1,wherein the step of forming the absorber layer comprises a cyclicaldeposition process.
 12. The method of claim 1, further comprisingforming an EUV photoresist layer overlying the absorber layer.
 13. Themethod of claim 1, wherein the step of forming the absorber layercomprises atomic layer deposition.
 14. The method of claim 1, furthercomprising forming an adhesion layer overlying the absorber layer tolimit outgassing from the adhesion layer and facilitate adhesion of theabsorber layer to the EUV photoresist layer.
 15. The method of claim 16,wherein the adhesion layer comprises SiOC.
 16. A structure for formingpatterned features using extreme ultraviolet (EUV) radiation, thestructure comprising: a substrate; and an absorber layer formedoverlying the substrate, wherein the absorber layer comprises an oxideof I, Te, Cs, Sb, Sn, In, Bi, Ag, Pb, Au, Pt, or Ir.
 17. A structure forforming patterned features using extreme ultraviolet (EUV) radiation,the structure comprising: a substrate; an underlayer formed overlyingthe substrate; and a dopant layer formed overlying or underlying theunderlayer to increase EUV sensitivity, wherein the dopant layercomprises at least one of a moderate EUV absorption dopant with an EUVcross section (σ_(α)) of greater an EUV cross section (σ_(α)) of oxygenand a high EUV absorption dopant with an EUV cross section (σ_(α)) ofgreater than 2×10⁶ cm²/mol.
 18. The structure according to claim 17,wherein the dopant layer comprises at least one of a moderate EUVabsorption dopant selected from the group consisting of Mn, Fe, Co, Ni,Cu, Zn, Ga, Ge, Hf, and As.
 19. The structure according to claim 18,wherein the high EUV absorption dopant is selected from the groupconsisting of I, Te, Cs, Sb, Sn, In, Bi, Ag, Pb, Au, Pt, and Ir.
 20. Thestructure according to claim 17, wherein the underlayer comprises anoxide of an element selected from the group consisting of I, Te, Cs, Sb,Sn, In, Bi, Ag, Pb, Au, Pt, and Ir.